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.TH XScreenSaver 3 __vendorversion__
.SH NAME
XScreenSaver \- X11 Screen Saver extension client library
.SH SYNOPSIS
.B #include <X11/extension/scrnsaver.h>
.PP
.nf
.ta .5i 2i
typedef struct {
    Window window;                /\(** screen saver window */
    int state;                    /\(** ScreenSaver{Off,On,Disabled} */
    int kind;                     /\(** ScreenSaver{Blanked,Internal,External} */
    unsigned long til_or_since;   /\(** milliseconds */
    unsigned long idle;           /\(** milliseconds */
    unsigned long event_mask;     /\(** events */
.br
} XScreenSaverInfo;

typedef struct {
    int type;               /\(** of event */
    unsigned long serial;   /\(** # of last request processed by server */
    Bool send_event;        /\(** true if this came frome a SendEvent request */
    Display *display;       /\(** Display the event was read from */
    Window window;          /\(** screen saver window */
    Window root;            /\(** root window of event screen */
    int state;              /\(** ScreenSaver{Off,On,Cycle} */
    int kind;               /\(** ScreenSaver{Blanked,Internal,External} */
    Bool forced;            /\(** extents of new region */
    Time time;              /\(** event timestamp */
.br
} XScreenSaverNotifyEvent;
.fi
.HP
Bool XScreenSaverQueryExtension(Display *\fIdpy\fP,
int *\fIevent_basep\fP, int *\fIerror_basep\fP\^);
.HP
Status XScreenSaverQueryVersion(Display *\fIdpy\fP, int *\fImajor_versionp\fP,
int *\fIminor_versionp\fP\^);
.HP
XScreenSaverInfo *XScreenSaverAllocInfo(\^void\^);
.HP
Status XScreenSaverQueryInfo(\^Display *\fIdpy\fP, Drawable \fIdrawable\fP,
XScreenSaverInfo *\fIsaver_info\fP\^);
.HP
void XScreenSaverSelectInput(Display *\fIdpy\fP, Drawable \fIdrawable\fP,
unsigned long \fImask\fp\^);
.HP
void XScreenSaverSetAttributes(Display *\fIdpy\fP, Drawable \fIdrawable\fP,
int \fIx\fP,
int \fIy\fP,
unsigned int \fIwidth\fP,
unsigned int \fIheight\fP,
unsigned int \fIborder_width\fP,
int \fIdepth\fP,
unsigned int \fIclass\fP,
Visual *\fIvisual\fP,
unsigned long \fIvaluemask\fP,
XSetWindowAttributes *\fIattributes\fP\^);
.HP
void XScreenSaverUnsetAttributes(Display *\fIdpy\fP,
Drawable \fIdrawable\fP\^);
.HP
void XScreenSaverSaverRegister(Display *\fIdpy\fP, int \fIscreen\fP,
XID \fIxid\fP, Atom \fItype\fP\^);
.HP
Status XScreenSaverUnregister(Display *\fIdpy\fP, int \fIscreen\fP\^);
.HP
Status XScreenSaverGetRegistered(Display *\fIdpy\fP, int \fIscreen\fP,
XID *\fIxid\fP, Atom *\fItype\fP\^);
.PP
.SH DESCRIPTION
The X Window System provides support for changing the image on a
display screen after a user-settable period of inactivity to avoid
burning the cathode ray tube phosphors.
However, no interfaces are provided for the user to control the image
that is drawn.
This extension allows an external ``screen saver'' client to detect
when the alternate image is to be displayed and to provide the
graphics.
.PP
Current X server implementations typically provide at least one form of
``screen saver'' image.
Historically, this has been a copy of the X logo drawn against the
root background pattern.
However, many users have asked for the mechanism to allow them to
write screen saver programs that provide capabilities similar to those
provided by other window systems.
In particular, such users often wish to be able to display corporate
logos, instructions on how to reactivate the screen, and automatic
screen-locking utilities.
This extension provides a means for writing such clients.
.SS Assumptions
This extension exports the notion of a special screen saver window that is
mapped above all other windows on a display.
This window has the \fIoverride-redirect\fP attribute set so that it
is not subject to manipulation by the window manager.
Furthermore, the X identifier for the window is never returned by
\fBQueryTree\fP requests on the root window, so it is typically not
visible to other clients.
.PP
.B XScreenSaverQueryExtension
returns
.B True
if the
.I XScreenSaver
extension is available on the given display.
A client must call
.B XScreenSaverQueryExtension
before calling any other XScreenSaver function in order
to negotiate a compatible protocol version; otherwise the client will
get undefined behavior (XScreenSaver may or may not work).
.PP
If the extension is supported, the event number for
.I ScreenSaverNotify
events is returned in the value pointed to by \fIevent_base\fP.
Since no additional errors are defined by this extension, the results
of \fIerror_base\fP are not defined.
.PP
.B XScreenSaverQueryVersion
returns
.B True
if the request succeeded; the values of the major and minor protocol
versions supported by the server are returned in
.I major_versionp
and
.I minor_versionp .
.PP
.B XScreenSaverAllocInfo
allocates and returns an \fBXScreenSaverInfo\fP structure
for use in calls to \fBXScreenSaverQueryInfo\fP.
All fields in the structure are initialized to zero.
If insufficient memory is available, NULL is returned.
The results of this routine can be released using \fIXFree\fP.
.PP
.B XScreenSaverQueryInfo
returns information about the current state of the
screen server in \fIsaver_info\fP and a non-zero value is
returned.
If the extension is not supported, \fIsaver_info\fP is not changed and 0
is returned.
.br
The \fIstate\fP field specifies whether or not the screen saver is currently
active and how the \fItil-or-since\fP value should be interpreted:
.TP 4
.I Off
The screen is not currently being saved; \fItil-or-since\fP
specifies the number of milliseconds until the screen saver is expected to
activate.
.TP 4
.I On
The screen is currently being saved; \fItil-or-since\fP specifies
the number of milliseconds since the screen saver activated.
.TP 4
.I Disabled
The screen saver is currently disabled; \fItil-or-since\fP is zero.
.br
The \fIkind\fP field specifies the mechanism that either is currently being
used or would have been were the screen being saved:
.TP 4
.I Blanked
The video signal to the display monitor was disabled.
.TP 4
.I Internal
A server-dependent, built-in screen saver image was displayed; either no
client had set the screen saver window attributes or a different client
had the server grabbed when the screen saver activated.
.TP 4
.I External
The screen saver window was mapped with attributes set by a
client using the \fBScreenSaverSetAttributes\fP request.
.PP
The \fIidle\fP field specifies the number of milliseconds since the last
input was received from the user on any of the input devices.
.br
The \fIevent-mask\fP field specifies which, if any, screen saver
events this client has requested using \fBScreenSaverSelectInput\fP.
.PP
.B XScreenSaverSelectInput
asks that events related to
the screen saver be generated for this client.
If
no bits are set in \fIevent-mask\fP, then no events will be generated.
Otherwise, any combination of the following bits may be set:
.TP 8
.B ScreenSaverNotify
If this bit is set, \fBScreenSaverNotify\fP events are generated whenever
the screen saver is activated or deactivated.
.TP 8
.B ScreenSaverCycle
If this bit is set, \fBScreenSaverNotify\fP events are generated whenever
the screen saver cycle interval passes.
.PP
.B XScreenSaverSetAttributes
sets the attributes to be used
the next time the external screen saver is activated.
If another client currently has the attributes set,
a BadAccess error is generated and the request is ignored.
.br
Otherwise, the specified window attributes are checked as if
they were used in a core \fBCreateWindow\fP request whose
parent is the root.
The \fIoverride-redirect\fP field is ignored as it is implicitly set
to True.
If the window attributes result in an error according to the rules for
\fBCreateWindow\fP, the request is ignored.
.br
Otherwise, the attributes are stored and will take effect on the next
activation that occurs when the server is not grabbed by another client.
Any resources specified for the
\fIbackground-pixmap\fP or \fIcursor\fP attributes may be
freed immediately.
The server is free to copy the \fIbackground-pixmap\fP or \fIcursor\fP
resources or to use them in place; therefore, the effect of changing
the contents of those resources is undefined.
If the specified \fIcolormap\fP no longer exists when the screen saver
activates, the parent's colormap is used instead.
If no errors are generated by this request, any previous screen saver
window attributes set by this client are released.
.br
When the screen saver next activates and the server is not grabbed by
another client, the screen saver window is
created, if necessary, and set to the specified attributes and events
are generated as usual.
The colormap associated with the screen saver window is installed.
Finally, the screen saver window is mapped.
.br
The window remains mapped and at the top of the stacking order
until the screen saver is deactivated in response to activity on
any of the user input devices, a \fBForceScreenSaver\fP request with
a value of Reset, or any request that would cause the window to be
unmapped.
.br
If the screen saver activates while the server is grabbed by another
client, the internal saver mechanism is used.
The \fBForceScreenSaver\fP request may be used with a value of Active
to deactivate the internal saver and activate the external saver.
.br
If the screen saver client's connection to the server is broken
while the screen saver is activated and the client's close down mode has not
been RetainPermanent or RetainTemporary, the current screen saver
is deactivated and the internal screen saver is immediately activated.
.br
When the screen saver deactivates, the screen saver window's colormap
is uninstalled and the window is unmapped (except as described below).
The screen saver XID is disassociated
with the window and the server may, but is not required to,
destroy the window along with any children.
.br
When the screen saver is being deactivated and then immediately
reactivated (such as when switching screen savers), the server
may leave the screen saver window mapped (typically to avoid
generating exposures).
.PP
.B XScreenSaverUnsetAttributes
instructs the server to discard
any previous screen saver window attributes set by this client.
.PP
.B XScreenSaverRegister
stores the given \fIXID\fP in the \fB_SCREEN_SAVER_ID\fP
property (of the given \fItype\fP) on the
root window of the specified \fIscreen\fP.
It returns zero if an error is encountered and the property is not
changed, otherwise it returns non-zero.
.PP
.B XScreenSaverUnregister
removes any \fB_SCREEN_SAVER_ID\fP from the
root window of the specified \fIscreen\fP.
It returns zero if an error is encountered and the property is
changed, otherwise it returns non-zero.
.PP
.B XScreenSaverGetRegistered
returns the \fIXID\fP and \fItype\fP stored in
the \fB_SCREEN_SAVER_ID\fP property on the
root window of the specified \fIscreen\fP.
It returns zero if an error is encountered or if the property does not
exist or is not of the correct format; otherwise it returns non-zero.
.SH "ERRORS"
.B XScreenSaverSelectInput,
.B XScreenSaverQueryInfo,
.B XScreenSaverSetAttributes 
and
.B XScreenSaverUnsetAttributes 
will generate a
.I BadDrawable
error if \fIdrawable\fP is not a valid drawable identifier.
If any undefined bits are set in \fIevent-mask\fP,
a BadValue error is generated by 
.B XScreenSaverSelectInput .
.PP
.SH "SEE ALSO"
Xlib(1), X(7)
.SH AUTHORS
Jim Fulton and Keith Packard.
.SH STABILITY
This API is considered as experimental.
The Xss library major revision may be incremented whenever
incompatible changes are done to the API without notice.
Use with care.
